Accession Number:

ADA278099

Title:

Numerical Model of the Thermal Behavior of an Extremity in a Cold Environment Including Counter-Current Heat Exchange between the Blood Vessels.

Descriptive Note:

Technical rept.,

Corporate Author:

ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA

Personal Author(s):

• Shitzer, Avraham
• Stroschein, Leander A.
• Vital, Paul
• Gonzales, Richard R.
• Pandolf, Kent B.

Report Date:

1994-03-01

Pagination or Media Count:

121.0

Abstract:

A numerical model of the thermal behavior of an extremity, e.g., finger, is presented. The model includes the effects of a heat conduction b metabolic heat generation, c heat transport by blood perfusion, d heat exchange between the tissue and the large blood vessels, and, e arterio-venous heat exchange. Heat exchange with the environment through a layer of thermal insulation, depicted by thermal handwear is also considered. The tissue is subdivided into four concentric layers. The layers described, from the center outward, as core, muscle, fat and skin. Differential heat balance equations are formulated for the tissue and the major artery and the major vein. These coupled equations are solved numerically by the alternating direction method employing a Thomas algorithm. The numerical scheme was tested extensively for stability and convergence. Results of the convergence tests are presented and discussed and the dependence on the number of grid points is demonstrated. Plots of tissue and blood temperatures along selected nodes of the model are shown for different combinations of parameters. The effect of counter-current heat exchange between the artery and the vein on the thermal balance of the extremity is presented. This shows clearly the conservation of energy achieved due to this mechanism. The report is concluded by considering the effects of cold induced vasodilation on tissue temperature cycling. Numerical model, Physiological model, Extremity model, Countercurrent, Heat exchange, Blood profusion, Heat conduction, Cold induced vasodilation, Heat balance, Alternating direction method, Thomas algorithm, Thermal insulation, Cold.

Descriptors:

• *HEAT EXCHANGERS
• *PHYSIOLOGICAL EFFECTS
• *THERMAL STRESSES
• *BLOOD VESSELS
• TEST AND EVALUATION
• ALGORITHMS
• TEMPERATURE
• STABILITY
• ENVIRONMENTS
• CORES
• TRANSPORT
• NUMBERS
• EQUATIONS
• CONSERVATION
• MUSCLES
• FATS
• BEHAVIOR
• HUMAN BODY
• CONVERGENCE
• BALANCE
• FINGERS
• COUNTERS
• BODY TEMPERATURE
• EXTREMITIES
• VASODILATION
• PERFUSION
• THERMAL INSULATION
• ARTERIES
• GLOVES
• HAZARDOUS MATERIALS
• VEINS
• BLOOD
• HEAT BALANCE
• NODES
• MODELS
• LAYERS
• PARAMETERS
• INSULATION
• ENERGY
• GRIDS

Subject Categories:

• Anatomy and Physiology
• Stress Physiology
• Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE